It's actually possible the real drop in users (or usage) might be more. Facebook took the front page (the whole effing page) of every news paper in India last week to alleviate fears. It's only comparable to DDG articles if Google also similarly had to put ads about how Google respects privacy because of an Exodus.
Sri Lankan here (that island under India). You would assume that this would go right over our heads, but a lot of people here are concerned and when I finally installed Signal, I noticed many people already there. Some of them, I never expected to see outside of WhatsApp or Viber.
Facebook was already pushing out long video ads on Indian TV, even before this fiasco. Indian consumers are seemingly more valuable; there are a significant number of users who use WhatsApp for business (customer support & sales). WhatsApp has also started a mobile payments platform in the country.